Harvey,
I disagree with this analysis. I am pretty sure that the limitation applies to the actual tongue (hitch) weight before you apply the equalization.
There are a couple of reasons I believe this. First, it's virtually impossible for a driver to measure how much weight is being transfered to the trailer tires and the truck's front axle by the equalizing hitch. The only way I know to measure this (other than extreme measures, like putting a strain gauge on the hitch ball) is by getting a series of weights of various axles with the trailer hitched and unhitched. Too hard. Therefore, I believe that Dodge set the limitation to mean the hitch weight of the unhitched trailer.
Second, the way an equalizing hitch works will increase, rather than decrease, the downward force on the hitch ball. This is what creates the moment (torque) that increases the weight on the truck's front axle. (It simultaneously increases the weight on the trailer's axles, but it's not necessary to study that to understand how the force is increased. )
Imagine yourself at the rear hitch instead of the trailer. How would you duplicate the forces that the trailer puts on the hitch? You would put a foot on the hitch ball and pull up on the equalizing bars while pushing down with your foot. This will increase the downward force on the hitch.
Dodge doesn't explain the reasons behind the hitch limitations, but I expect they allow a larger downward force (hitch weight) with an equalizing hitch because of two things.
First, the hitch mounting is stressed differently when using an equalizing hitch. The forward hitch mounts are under compression and the rear mounts are under tension if no equalizing is used. This situation is more or less reversed when you use an equalizing hitch.
Second, without an equalizing hitch, weight is removed from the truck's front axle. This can result in less effective steering. An equalizing hitch does the opposite, increasing the weight on the truck's front axle.
I would take the published limitations at face value and not try to read too much into them.
Loren,
I won't dispute your argument about whether the Dodge factory hitch receiver max rated weight is intended to be with or without trailer tongue weight actually resting on the hitch. I don't remember whether, or if, I have ever read anything in writing from a manufacturer. I'll allow that statement to go unchallenged now. However, more later... ... ...
I will definitely dispute your theory about where the weight is redistributed to when the torsion bars are installed and tensioned on a weight distributing hitch. You are completely mistaken about that.
Think about it. Weight distributing hitches were first introduced back in the 1950s or 1960s when people were towing small to medium sized travel trailers with ordinary cars, Suburbans, or 1/2 ton pickups of the period.
Those tow vehicles were not capable of handling the tongue weight of a travel trailer resting on a ball 3' to 4' behind the rear axle. The weight sagged their rear ends badly, transfered weight from the steering axles leaving a dangerous condition for handling, and pointed their headlights into the sky.
The fundamental purpose of a weight distributing hitch was to ... ... ... distribute weight. The torsion bars transferred the tongue weight which the tow vehicle couldn't handle back to the trailer axles and forward to the unloaded steer axle. A tow vehicle-trailer combination properly set up with a properly matched and adjusted WD hitch assembly was restored to level towing height.
The way to understand how a WD hitch works is to ignore the trailer ... just assume the ball is overloaded and the rear of the tow vehicle is sagging. Now think of inserting the torsion bars into the hitch head and lifting the weight like you would lift the arms of a wheelbarrow. You lift the bars and the rear end of the tow vehicle is returned to level. You with me?
Okay, the excess weight is supported by a human and the tow vehicle is level but what to do with the weight? Where do you hang the weight to maintain the level condition? Now, in your mind, put the trailer back in place behind the tow vehicle with it's ball coupler resting on the ball.
Simply hang each torsion bar on the flip over bracket on each side of the trailer A frame. Properly adjusted the trailer flipover brackets now support the weight. And where is the weight distributed? Aft to the trailer axles and forward to the tow vehicle's steer axles. Simple and effective and in use for 50-60 years.
That is the way a weight distributing hitch works. If you doubt me find an old guy (nobody younger than 50 or 60 will know) who owns a trailer dealership and who has owned it since the 1960s or an RV mechanic who has worked on them since the 1960s. Or better yet, find the owner's manual for an old Airstream or an old Reese hitch. You will find that I am correct. Been there, done that.
I've owned and pulled travel trailers since I bought my first, a 1973 Fleetwood Prowler 23' or 24' (can't remember which, now) in Bremerton, Washington in late fall of 1972. I've owned and pulled them continuously ever since except for the five years I spent in the Philippines near the end of my Navy career. I owned a 35' travel trailer during that period but it was in storage in San Diego.
Now, if you're still with me, you'll see why I say that what matters in the matter of rated weight on the hitch receiver is actual tongue weight with WD bars installed, not empty weight, because towing weight is what is actually resting on the hitch receiver and it is always less than tongue weight when properly set up. Tongue weight without bars installed is not going to be towing weight therefore it is only theoretical.
And last, it is not "virtually impossible" to measure the amount of weight transferred. It is not even difficult. In truth the actual weight in pounds is irrelevant. What it is is what it is. What matters is how it is distributed.
You simply measure the distance from pavement to front bumper or other convenient measure point on the unloaded tow vehicle and take the same measurement at the rear. Then, you back up to the tow vehicle and drop the ball coupler on the ball and watch the rear end sag. Then, using the electric tongue jack of a premium trailer you lift the rear of the tow vehicle and the front of the trailer well above level to allow for the spring in the WD bars. Install the WD bars, adjust the links, lower the jack, and take your measurements again. If necessary lift the truck and trailer again and select different links in the chains and try again. Your goal is to get the tow combination level and return the front towing height to a point slightly lower than the original, and the tow combination is properly set up for towing.
Generally speaking you would want the front and rear of the tow vehicle to drop slightly front and back but not below level at the rear of a pickup because an unloaded pickup always has about a 60% to 40% front to rear weight distribution when unloaded. Closer to 50% to 50% is desired.
I can't give precise adjustment instructions because the details depend on the tow vehicle, its suspension, and the trailer's weight. Beginning in the '70s I always towed with a 3/4 ton pickup so my spring compression rates were considerably less than those towing with a car or 1/2 ton. The stiffer the suspension, the less spring deflection that will occur.
When I transported RVs commercially the companies generally demanded the use of WD bars because the office staff didn't know which end of the trailer was supposed to be coupled to the truck and they thought the purpose of a WD hitch was to control sway. I ignored them and never used a WD hitch on even the largest, heaviest conventional travel trailers because I pulled a lot on rain slicked highways or on snow and ice and I wanted the weight on the rear tires of my dually pickups.
Hope this explanation helps. If you doubt me ask Reese or an old timer.